1.\" $OpenBSD: pthread_once.3,v 1.8 2001/06/24 23:46:35 jasoni Exp $ 2.\" Copyright (c) 1996 John Birrell <jb@cimlogic.com.au>. 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 3. All advertising materials mentioning features or use of this software 14.\" must display the following acknowledgement: 15.\" This product includes software developed by John Birrell. 16.\" 4. Neither the name of the author nor the names of any co-contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" $FreeBSD: pthread_once.3,v 1.5 1999/08/28 00:03:09 peter Exp $ 33.\" 34.Dd April 4, 1996 35.Dt PTHREAD_ONCE 3 36.Os 37.Sh NAME 38.Nm pthread_once 39.Nd dynamic package initialization 40.Sh SYNOPSIS 41.Fd #include <pthread.h> 42.Pp 43.Ft pthread_once_t 44.Fa once_control 45\&= 46.Dv PTHREAD_ONCE_INIT ; 47.Pp 48.Ft int 49.Fn pthread_once "pthread_once_t *once_control" "void (*init_routine)(void)" 50.Sh DESCRIPTION 51The first call to 52.Fn pthread_once 53by any thread in a process, with a given 54.Fa once_control , 55will call the 56.Fn init_routine 57with no arguments. Subsequent calls to 58.Fn pthread_once 59with the same 60.Fa once_control 61will not call the 62.Fn init_routine . 63On return from 64.Fn pthread_once , 65it is guaranteed that 66.Fn init_routine 67has completed. The 68.Fa once_control 69parameter is used to determine whether the associated initialization 70routine has been called. 71.Pp 72The function 73.Fn pthread_once 74is not a cancellation point. However, if 75.Fn init_routine 76is a cancellation point and is cancelled, the effect on 77.Fa once_control is as if 78.Fn pthread_once 79was never called. 80.Pp 81The constant 82.Dv PTHREAD_ONCE_INIT 83is defined by header 84.Aq Pa pthread.h . 85.Pp 86The behavior of 87.Fn pthread_once 88is undefined if 89.Fa once_control 90has automatic storage duration or is not initialized by 91.Dv PTHREAD_ONCE_INIT . 92.Sh RETURN VALUES 93If successful, the 94.Fn pthread_once 95function will return zero. Otherwise an error number will be returned to 96indicate the error. 97.Sh ERRORS 98None. 99.Sh STANDARDS 100.Fn pthread_once 101conforms to ISO/IEC 9945-1 ANSI/IEEE 102.Pq Dq Tn POSIX 103Std 1003.1 Second Edition 1996-07-12. 104